External fixation system with radio frequency shielding

ABSTRACT

An electrical insulator is applied to a bone anchor, for instance of a bone implant, such as an external fixation frame, so as to prevent undesirable temperature increases in the bone anchor and surrounding anatomical tissue when subjected magnetic resonance imaging.

CROSS-REFERENCE TO RELATED APPLICATIONS

This claims priority to U.S. patent application Ser. No. 13/837,598filed Mar. 15, 2013, the disclosure of which is hereby incorporated byreference as if set forth in its entirety herein.

BACKGROUND

Bone fixation systems can include external bone fixation systems thatare typically attached to two or more bone members so as to stabilizethe bone members and promote healing. The external bone fixation systemscan be applied to treat comminuted, intra-articular and/or unstablefractures. Thus, the bone members can be fractured segments of a bone,or can alternatively be two different bones, for instance vertebrae,that are to be stabilized relative to each other. Typical externalfixation systems can include a plurality of bone anchors that areconfigured to be driven through the dermal surface and into respectivebone members. For instance, the bone anchors typically are configured asbone screws, such as Schanz screws, that have a length sufficient suchthat they extend out from the epidermis when anchored in the respectivebone members.

External fixation systems can further include at least one support rod,and at least one set of clamps that are configured to be secured to boththe rod and the bone anchors, directly or indirectly, at a locationoutside the dermal surface, thereby securing the bone anchors relativeto the rod, and supporting each the bone fixation members relative tothe other bone fixation members that are secured to the rod. Externalfixation system can further include clamps that are configured to besecured to a pair of rods, so as to secure each of the pair of rods tothe other. External fixation systems further commonly include couplingmembers that are configured to attach to both the support rod and one ormore of the Schanz screws, such that the Schanz screws, and thus thebone members, are supported by the rod in fixation with the respectivebone members.

Conventional support rods, clamps, and bone fixation members aretypically made from an electrically and thermally conductive materialstainless steel, titanium, alloys thereof, or any suitable alternativemetal. Though support rods can be made from a non-ferromagneticmaterial, such as such as aluminum or carbon, the external fixationsystem in combination with the soft tissue into which the externalfixation system is implanted can define a closed electrical loop. As aresult, when the external fixation system is subjected to the magneticfields (typically having a strength between and including 1.5 Tesla and3.0 Tesla, but can range up to and including 8.0 Tesla) and radiofrequency pulses of a magnetic resonance imaging (MRI) system,electrical current can be induced in the closed electrical loop. Thecurrent flow can cause the temperature of the thermally conductiveSchanz screws to rise substantially inside the patient's body, resultingin pain and damage to the tissue.

External fixation systems have been proposed that are said to reduce orprevent current when the implanted exposed to the RF field of an MRI.For instance, U.S. Pat. No. 7,527,626 discloses that the rod and/orclamps can include a carbon core and a polymeric insulation sheath thatis applied onto the carbon core through resin transfer molding. Thepatent recognizes that the size of the carbon core of the rod “must” bereduced so that once the sheath is applied to it, the resulting producthas the same size as rods typically used in external fixation systems.Accordingly, the core is made of a higher modulus carbon fiber. Thus,the sheath can add cost and complexity to the manufacture of theexternal fixation system

SUMMARY

In accordance with one embodiment, an external fixation system includesa first Schanz screw including a first shaft that defines a firstexternal surface that is devoid of threads. The first Schanz screw canfurther include a first threaded region that extends from the firstshaft, the first threaded region presenting external threads that areconfigured to be anchored into bone. The external fixation system canfurther include a second Schanz screw including a second shaft thatdefines a second external surface that is devoid of threads. The secondSchanz screw can further include a second threaded region that extendsfrom the second shaft, the second threaded region presenting externalthreads that are configured to be anchored into bone. The externalfixation system can further include at least one support rod thatcomprises an electrically conductive material. The external fixationsystem can further include a first clamp configured to attach to boththe first shaft and the at least one support rod, and a second clampconfigured to attach to both the second shaft and the at least onesupport rod, thereby fixedly supporting each of the first and secondSchanz screws relative to the at least one support rod. At least thefirst Schanz screw can include a layer of electrically insulativematerial that is attached to at least a portion of the first externalsurface and is not attached to the first threaded region.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofillustrative embodiments of spreader system of the present application,will be better understood when read in conjunction with the appendeddrawings. For the purposes of illustrating the spreader system of thepresent application, there is shown in the drawings illustrativeembodiments. It should be understood, however, that the application isnot limited to the precise arrangements and instrumentalities shown. Inthe drawings:

FIG. 1 is a perspective view of an external fixation system shownanchored into bone;

FIG. 2A is a sectional perspective view of a portion of the externalfixation system illustrated in FIG. 1, taken along line 2A-2A;

FIG. 2B is a sectional perspective view of a portion of the externalfixation system illustrated in FIG. 1, taken along line 2B-2B;

FIG. 3A is a perspective view of first Schanz screw of the externalfixation system constructed in accordance with one embodiment;

FIG. 3B is a perspective view of first Schanz screw of the externalfixation system constructed in accordance with another embodiment;

FIG. 3C is a plan view of a tape of the first Schanz screw illustratedin FIG. 3A;

FIG. 4A is a perspective view of the external fixation system asillustrated in FIG. 1, but constructed in accordance with anotherembodiment;

FIG. 4B is a perspective view of the external fixation system asillustrated in FIG. 1, but constructed in accordance with yet anotherembodiment:

FIG. 4C is a perspective view of the external fixation system asillustrated in FIG. 1, but constructed in accordance with still anotherembodiment;

FIG. 4D is a perspective view of the external fixation system asillustrated in FIG. 1, but constructed in accordance with still anotherembodiment;

FIG. 5A is a schematic illustration of a patient disposed in an MRItube, wherein an external fixation system is attached to an anatomy ofthe patient and disposed in the MRI tube; and

FIG. 5B is a schematic illustration of a patient disposed in an MRItube, wherein an external fixation system is attached to an anatomy ofthe patient and disposed outside the MRI tube.

DETAILED DESCRIPTION

Certain terminology is used in the following description for convenienceonly and is not limiting. The words “right”, “left”, “lower” and “upper”designate directions in the drawings to which reference is made. Thewords “inner” or “distal” and “external” or “proximal” refer todirections toward and away from, respectively, the geometric center ofthe implant and related parts thereof. The words, “anterior”,“posterior”, “superior,” “inferior,” “medial,” “lateral,” and relatedwords and/or phrases are used to designate various positions andorientations in the human body to which reference is made and are notmeant to be limiting. The terminology includes the above-listed words,derivatives thereof and words of similar import.

Referring to FIG. 1, a bone implant can be configured as a bone fixationsystem. The bone fixation system, in turn, can be configured as anexternal bone fixation system, also referred to as an external fixationsystem 20, that is configured to stably support a first bone member 22 arelative to a second bone member 22 b. The first and second bone members22 a and 22 b can be of the same bone or of different bones. Inaccordance with the embodiment illustrated in FIG. 1, the first andsecond bone members 22 a-b are bone segments of a bone 22, such as along bone, and are separated from each other by a bone gap 22 c, such asa fracture, of the bone 22. The external fixation system 20 can includea first at least one external fixation bone anchor 24 configured toattach to bone, for instance at the first bone member 22 a, and a secondat least one external fixation bone anchor 26 configured to attach tobone, for instance at the second bone member 22 b. In accordance withthe illustrated embodiment, the at least one bone anchor 24 can includefirst and second bone anchors 24 a and 24 b that are configured toattach to the same bone member, for instance to the first bone member 22a, and the at least one bone anchor 26 can include first and second boneanchors 26 a and 26 b that are configured to attach to the same bonemember, for instance to the second bone member 22 b.

Thus, it should be appreciated that the external fixation system 20 caninclude at least a first bone anchor and a second bone anchor that areconfigured to be anchored into bone. The first and second bone anchorscan be anchored into the same bone member (e.g., first and second boneanchors 24 a and 24 b, and first and second bone anchors 26 a and 26 b),or can be anchored into different bone members (e.g., first bone anchor24 a and second bone anchor 26 b, and first bone anchor 26 a and secondbone anchor 24 b). In accordance with the illustrated embodiment, eachof the external fixation bone anchors 24 and 26 can be configured asscrews, such as Schanz screws or K-wires, and can include a shaft 30that defines an external surface 32 (see also FIG. 2A) that can bedevoid of threads, and a threaded region 34 that extends from the shaft30, the threaded region 34 presenting external threads 36 that areconfigured to be anchored into bone so as to anchor the threaded region34 into bone. The first and second at least one bone anchors 24 and 26are constructed such that, when the threaded regions 34 are driven intobone, the shafts 30 extend out from the epidermis 23 (see FIGS. 5A-5B).While the first and second at least one bone anchors 24 and 26 areillustrated as including the threaded region 34, it should beappreciated that the first and second at least one bone anchors 24 and26 can alternatively be configured as pins that are devoid of threadedregions.

While the illustrated embodiment includes first and second anchors 24 aand 24 b attached to the first bone member 22 a and first and secondbone anchors 26 a and 26 b attached to the second bone member 22 b, itshould be appreciated that the external fixation system can include anynumber of bone anchors, such as one or a plurality of bone anchors, thatare configured to attach to the first and second bone members 22 a and22 b as desired. As will be appreciated from the description below, atleast one, such as a plurality, up to all, of the bone anchors 24 and 26can include at least one layer of electrically insulative materialattached to at least a portion of the respective external surface 32,such that the electrically insulative material is not attached to therespective threaded region 34.

The external fixation system 20 can further include at least one supportrod 38 that extends from a first location aligned with the first bonemember 22 a and across the bone gap 22 c to a second location alignedwith the second bone member 22 b. The at least one support rod 38 isconfigured to be fixedly secured relative to the bone anchors 24 and 26.For instance, the at least one support rod 38 can include a firstsupport rod 38 a, a second support rod 38 b, and a third support rod 38c. The first and second bone anchors 24 a and 24 b can be attached tothe first support rod 38 a, and the first and second bone anchors 26 aand 26 b can be attached to the second support rod 38 b. Each of thefirst rod 38 a and the second rod 38 b can be attached to the thirdsupport rod 38 c, such that the first and second rods 38 a and 38 b arefixedly secured relative to each other. Because the bone anchors 24 canbe fixedly secured to the first support rod 38 a, and the bone anchors26 can be fixedly secured to the second support rod 38 b, the boneanchors 24 and 26 can be fixedly secured relative to each other. Whilethe bone anchors 24 and 26 are illustrated as being attached to thefirst and second support rods 38 a and 38 b, respectively, it should beappreciated that the bone anchors 24 and 26 can alternatively beattached and fixedly secured to a single support rod that spans acrossthe bone gap 22 c. It should be appreciated that the support rods 38 canbe disposed outside the epidermis 23 when attached to the respectiveexternal fixation bone anchors.

The external fixation system 20 can further include a first at least onefirst clamp 40 configured to attach to a first one of the bone anchors24 a-b and 26 a-b, and a second at least one clamp 42 configured toattach to a second one of the bone anchors 24 a-b and 26 a-b. The firstand second at least one clamps 40 and 42 are further configured toattach to the at least one support rod 38 so as to fixedly secure theattached bone anchors to the at least one support rod 38. In accordancewith the illustrated embodiment, the first at least one clamp 40 caninclude a first clamp 40 a and a second clamp 40 b that are eachconfigured to attach to any of the bone anchors 24 and 26. In accordancewith the illustrated embodiment, the first clamp 40 a is attached to thefirst bone anchor 24 a and the second clamp 40 b is attached to thesecond bone anchor 24 b. Further, in accordance with the illustratedembodiment, the second at least one clamp 42 can include a first clamp42 a and a second clamp 42 b that are each configured to attach to anyof the bone anchors 24 and 26. In accordance with the illustratedembodiment, the first clamp 42 a is attached to the first bone anchor 26a and the second clamp 42 b is attached to the second bone anchor 26 b.As will be appreciated from the description below, the clamps 40 and 42are configured to attach to the respective bone anchors 24 and 26 at therespective shafts 30, for instance at the respective unthreaded externalsurfaces 32. As described above, the bone anchors 24 and 26 areconstructed such that, when the threaded regions 34 are driven intobone, the shafts 30 extend out from the epidermis 23 (see FIGS. 5A-5B).Thus, the clamps 40 and 42 can be disposed outside the epidermis 23.

Each of the clamps 40 and 42 can be configured to attach to the at leastone support rod 38. For instance, each of the clamps 40 and 42 can beconfigured to attach to each of the first and second support rods 38 aand 38 b. In accordance with the illustrated embodiment, the first clamp40 a is attached to the first support rod 38 a, and the second clamp 40b is attached to the first support rod 38 a. The clamps 40 can betightened to the respective bone anchors 24 and the first support rod 38a so as to be fixedly secured to the respective bone anchors 24 and tobe fixedly secured to the first support rod 38 a. Further, in accordancewith the illustrated embodiment, the first clamp 42 a is attached to thesecond support rod 38 b, and the second clamp 42 b is attached to thesecond support rod 38 b. The clamps 42 can be tightened to therespective bone anchors 26 and the second support rod 38 b so as to befixedly secured to the respective bone anchors 26 and to be fixedlysecured to the second support rod 38 b. In an embodiment where the atleast one support rod 38 defines a single support rod, each of theclamps 40 and 42 can be configured to be attached and fixedly secured tothe single support rod at different locations along the single supportrod.

With continuing reference to FIG. 1, the external fixation system 20 caninclude a bridge 44 that is configured to fixedly secure the first andsecond support rods 38 a and 38 b relative to each other. The bridge 44can include the third support rod 38 c, and at least one third claimthat can include a first clamp 48 a configured to attach to both thethird support rod 38 c and the first support rod 38 a, and a secondclamp 48 b configured to attach to both the third support rod 38 c andthe second support rod 38 b. In particular, each of the first and secondclamps 48 a and 48 b can define respective first and second channels 49a and 49 b. The channel 49 a and 49 b can be oriented substantiallyparallel or angularly offset with respect to each other as desired, andcan be sized, so as to respectively receive the third support rod 38 cand a corresponding one of the first and second support rods 38 a and 38b. The clamps 48 a and 48 b can be tightened to the respective thirdsupport rod 38 c and the corresponding first and second support rods 38a and 38 b, so as to fixedly secure the third support rod 38 c withrespect to the first and second support rods 38 a and 38 b, therebyfixedly securing the first and second support rods 38 a and 38 b to eachother.

Referring now to FIGS. 2A-2B, the clamp 40 a is illustrated, it beingappreciated that the clamp 40 a can be representative of one or more upto all of the clamps 40 b and 42 a-b. Thus, the description of the clamp40 a can apply to all other clamps of the external fixation system 20 asdesired. The clamp 40 a can include a clamp body 50 that defines firstand second channels 52 a and 52 b. The first channel 52 a is configuredto receive the corresponding bone anchor, such as the bone anchor 24 a,for instance at the shaft portion 30. For instance, the clamp body 50can include a first inner surface 54 that defines the first channel 52a. The inner surface 54 can be tightened against the shaft 30 so as tofixedly secure the bone anchor 24 a to the clamp 40 a. In accordancewith one embodiment, the inner surface 54 can be defined by first andsecond clamp members 56 a and 56 b of the clamp body 50. The first andsecond clamp members 56 a and 56 b can be biased together so as totighten the inner surface 54 against the shaft 30. It should beappreciated that the inner surface 54 can be textured so as to increasethe grip of the inner surface 54 relative to the shaft 30.

Similarly, the second channel 52 b is configured to receive the at leastone support rod 38, such as the corresponding first support rod 38 a.For instance, the clamp body 50 can include a second inner surface 58that defines the second channel 52 b. The second inner surface 58 can betightened against the shaft first support rod 38 a so as to fixedlysecure the first support rod 38 a to the clamp 40 a. In accordance withone embodiment, the inner surface 58 can be defined by third and fourthclamp members 60 a and 60 b of the clamp body 50. The third and fourthclamp members 60 a and 60 b can be biased together so as to tighten theinner surface 58 against the first support rod 38 a. It should beappreciated that the inner surface 58 can be textured so as to increasethe grip of the inner surface 58 against the shaft first support rod 38a.

In accordance with the illustrated embodiment, the clamp 40 a caninclude a tightener 63 having a head 64 and a shaft 66 that extends outfrom the head 64. The shaft 66 can carry threads 68 that mate withthreads 70 of a threaded surface 71 of the clamp body 50. The head 64 issized to abut an abutment surface 73 of the clamp body 52. The first andsecond inner surfaces 54 and 58 can be disposed between the abutmentsurface 73 and the threaded surface 71. Accordingly, as the tightener 63is rotated in a first direction relative to the clamp body 50, theabutment surface 73 and the threaded surface 71 are drawn toward eachother, thereby causing the inner surfaces 54 and 58 to compress againstthe shaft 30 and the first support rod 38 a, respectively, therebypreventing the bone anchor and the first support rod 38 a from movingwithin the respective channels 52 a and 52 b relative to the clamp body50. As the tightener 63 is rotated in a second direction relative to theclamp body 50 opposite the first direction, a gap between the head 64and the abutment surface 73 loosens the inner surfaces 54 and 58 fromthe shaft 30 and the first support rod 38 a, thereby allowing the boneanchor 24 and the first support rod 38 a to move within the respectivechannels 52 a and 52 b.

The at least one support rod 38, including the first support rod 38 a,the second support rod 38 b, and the third support rod 38 c, can all bemade of an electrically conductive material, and can be devoid of anyinsulating material, for instance at least at locations at and betweenthe first and second bone anchors described above, though it should beappreciated that the rods 38 a-c can include an insulating material asdesired. The clamps. 40, 42, and 48 can likewise be made from anelectrically conductive material, such as stainless steel, titanium, andalloys thereof. The clamps 40, 42, and 48 can also be devoid of aninsulating material, though it should be appreciated that the clamps 40,42, and 48 can include an insulating material as desired. Furthermore,while the external fixation system 20 has been described in accordancewith one embodiment, it is recognized that external fixation systems areavailable including any number of bone anchors, support rods, andcorresponding clamps, as desired, defining essentially any configurationand arrangement as desired. Thus, the present disclosure is not limitedto the external fixation system 20 described herein.

Referring now to FIGS. 3A-B, the first bone anchor 24 a is illustrated,it being appreciated that the bone anchor 24 a can be representative ofone or more up to all of the bone anchors 24 b and 26. Thus, thedescription of the bone anchor 24 a can apply to all other bone anchorsof the external fixation system 20 as desired. The bone anchor 24 can beelongate along a central axis 25, which can define an axial direction.The bone anchor 24 can include the shaft 30 that is elongate along thecentral axis 25 and the threaded region 34 that extends from the shaft30 and is elongate along the central axis 25. The external surface 32 ofat least a portion of the shaft can revolve about the first central axisThe bone anchor 24 can further include a tip 35 that extends from thethreaded region 34. The tip 35 can be tapered, and can include at leastone cutting flute that is configured to create an aperture into thebone. Alternatively, the bone anchor 24 can be devoid of cutting flutes.Thus, a hole can be pre-drilled into the bone, and the threaded regioncan be driven into the pre-drilled hole.

It should be appreciated that the shaft 30, the threaded region 34, andthe tip (if included) can be constructed to define any suitable size andshape as desired. For instance, the shaft 30 can define a firstoutermost cross-sectional dimension D1, which can be a diameter, along adirection perpendicular to the central axis 25. The threaded region 34can define a second outermost cross-sectional dimension D2, which can bea diameter, that is less than the first outermost cross-sectionaldimension D1. Alternatively the first outermost cross-sectionaldimension D1 can be substantially equal to the second outermostcross-sectional dimension D2. Alternatively still, the shaft 30 caninclude a first portion 31 a that defines the first outermostcross-sectional dimension D1, and a second portion 31 b that can definethe second outermost cross-sectional dimension D2.

The shaft 30 defines a first terminal end, such as a proximal end 30 a,and a second or distal end 30 b that is spaced from and opposite theproximal end 30 a along the central axis 25. The shaft 30 can define ashoulder 33 that defines an interface between the first portion 31 a andthe second portion 31 b. The proximal end 30 a can be defined by thefirst portion 31 a, and the distal end 30 b can be defined by the secondportion 31 b, such that the shoulder 33 is disposed between the proximalend 30 a and the distal end 30 b. Alternatively, the shaft 30 can bedevoid of the shoulder 33, and can define a substantially constantoutermost cross-sectional dimension D1 from the proximal end 30 a to thedistal end 30 b. The proximal end 30 a can define any suitableengagement member as desired that is configured to attach to a drivinginstrument that is configured to rotate the bone anchor 24 a so as todrive the threaded region 34 into the bone.

The threaded region 34 defines a proximal end 34 a and a distal end 34 bthat is spaced from and opposite the proximal end 34 a along the centralaxis 25. The proximal end 34 a can extend integrally and monolithicallyfrom the distal end 30 b, such that the threaded region 34 is integraland monolithic with the shaft 30. The tip 35, if present, can extendfrom the distal end 34 b so as to be integral and monolithic with eachof the threaded region 34 and the shaft 30. By way of example only, thebone anchor 24 a can define any length as desired along the central axis25 from the tip to the proximal end 30 a of the shaft, for instancewithin a range having a lower end of approximately 60 mm and an upperend of approximately 250 mm. The cross-sectional dimensions D1 and D2can be between approximately 2 mm and approximately 8 mm, includingapproximately 3 mm, approximately 4 mm, and approximately 5 mm.

With continuing reference to FIGS. 3A-3C, the bone anchor 24 a caninclude an electrically insulative material 84, which can be configuredas a layer 82 of electrically insulative material 84, that can beattached to at least a portion of the external surface 32, but not tothe threaded region 34. For instance, the layer 82 of electricallyinsulative material 84 can be adhesively attached to the at least aportion of the external surface 32. For example, the layer 82 can beattached to the external surface at a location between the shoulder 33and the proximal end 30 a. The layer 82 can, for instance, be receivedin the corresponding channel 52 a of the clamp 40 a as described above,such that the inner surface of the channel 52 a is tightened to thelayer 82 so as to fixedly secure the bone anchor 24 a therein.Alternatively, the inner surface of the channel 52 a can tightendirectly against the exterior surface 32 of the shaft 30, for instanceif the layer terminates at a location spaced from the inner surface ofthe channel 52 a.

In accordance with one embodiment, the electrically insulative material84 is configured as a tape 86 having a substrate 88 made from theelectrically insulative material 84, and an adhesive 90 disposed on onesurface 88 a of the substrate 88, such that the adhesive 90 attaches tothe external surface 32 so as to attach the tape 86 to the at least aportion of the external surface 32 of the shaft 30. The substrate 88,and thus the tape 86, can define the surface 88 a. Further, thesubstrate 88, and thus the tape 86, can define a second surface 88 bopposite the surface 88 a, such that the tape 86 defines a thicknessmeasured from the surface 88 a to the second surface 88 b along adirection perpendicular to the central axis 25. The thickness of thetape 86 can be between approximately 1 mil and approximately 6 mils, forinstance between approximately 2 mils and approximately 4 mils,including approximately 2.5 mils and approximately 3.5 mils. Thus, thethickness of the tape 86 can be between approximately 0.025 mm andapproximately 0.155 mm, for instance between approximately 0.05 mm andapproximately 0.1 mm, including approximately 0.0635 mm andapproximately 0.09 mm. In accordance with one embodiment, the thicknessof the tape 86 can be in a range having a lower end of 0.064 mm and 0.6mm. Thus, in one example, the thickness of the tape 86 can be defined asbeing within a range of approximately 0.5% and approximately 30% of thefirst outermost cross-sectional dimension D1 of the shaft 30. It shouldbe appreciated, however, that the tape 86 can have any thickness asdesired suitable for providing radio frequency shielding of thecorresponding bone anchor between the respective shaft and therespective threaded region in external fixation system. The smallthickness of the tape 86 can allow the cross-sectional dimension of theshaft 30 can be unchanged with respect to pre-existing bone anchorssuitable for inclusion in external fixation systems. As a result, theshaft 30 can include the same bending stiffness and torsional stabilityof pre-existing bone anchors suitable for inclusion in external fixationsystems without changing the material of the shaft 30. The electricallyinsulative material 84, and thus the tape 86, can be substantiallynonporous and non-ferromagnetic. For instance, in accordance with oneembodiment, the electrically insulative material 84 can be a polyimide,or any suitable alternative insulative material as desired.

The tape 86 can be wrapped around the at least a portion of the firstexternal surface 32 at least one entire revolution about the centralaxis 25. For instance, as illustrated in FIG. 3A, adjacent revolutions94 of the tape 86 along the central axis 25 can overlap each other withrespect to a line that extends through the tape 86 to the central axis25 along a direction perpendicular to the central axis. Alternatively,adjacent revolutions 94 of the tape 86 along the central axis 25 can bedisposed adjacent each other along a direction parallel to the centralaxis 25, such that the bone anchor 24 a does not define a line thatextends to the central axis along a direction perpendicular to thecentral axis and passes through adjacent revolutions 94 of the tape 86.The tape 86 can define a proximal end 86 a and a distal end 86 b thatcan define any suitable distance therebetween along the central axis 25.For instance, as illustrated in FIG. 3B, the distance can be suitablesuch that the tape 86 can be wrapped one revolution 94 about the centralaxis 25. For instance, the taps 86 can define opposed edges 86 c and 86d that can abut each other, or can overlap each other, for instance ifthe tape 86 extends more than one revolution 94 about the central axis25. Thus, it can be said that the tape 86 can make at least onerevolution 94 about the central axis 25 so as to attach the adhesive 90to the external surface 32. It should be appreciated that theelectrically insulative material 84 can be applied to the at least aportion of the external surface 32 of the shaft 30. For instance, theelectrically insulative material 84 can be sprayed onto the at least aportion of the external surface 32 of the shaft 30 and allowed to dry.As another example, the shaft 30 can be dipped into the electricallyinsulative material 84 in liquid form so as to apply the electricallyinsulative material 84 to the at least a portion of the external surface32 of the shaft 30, and the electrically insulative material 84 can beallowed to dry. It should be appreciated that the electricallyinsulative material 84 can be adhesively attached to the at least aportion of the external surface 32 of the shaft 30 when sprayed or whenthe at least a portion of the external surface 32 of the shaft 30 isdipped into the electrically insulative material 84. The electricallyinsulative material 84 can include polyimide along with a separateadhesive agent as desired. Alternatively, the polyimide can suitablyadhesively attach to the external surface 32 without inclusion of aseparate adhesive agent in the electrically insulative material 84.

Furthermore, existing bone anchors can be retrofit by applying theelectrically insulative material 84 to the respective shaft as describedherein so as to produce the bone anchor 24 a. Thus, a method can beprovided for fabricating an external fixation system of the type havingfirst and second Schanz screws, each including a shaft that defines anexternal surface that is devoid of threads, and a threaded region thatextends from the shaft, the threaded region presenting external threadsthat are configured to be anchored into a first bone member. The methodcan include the step of applying a layer of electrically insulativematerial to at least a portion of the external surface of the firstSchanz screw, such that the layer of electrically insulative material isattached to the threaded region of the first Schanz screw. Theelectrically insulative material can comprise a substrate having firstand second opposed surfaces, and an adhesive carried by the firstsurface, the applying step further comprises the step adhesivelyattaching the first surface to the at least a portion of the externalsurface of the first Schanz screw. The shaft of the first Schanz screwcan be elongate along a central axis, and the method can furthercomprising the step of attaching the first surface to the at least aportion of the external surface at least one revolution about thecentral axis. The shaft of the second Schanz screw can be elongate alonga central axis, and the method further comprising the step of attachingthe first surface to at least a portion of the external surface of thesecond Schanz screw at least one revolution about the central axis ofthe second Schanz screw.

Referring to FIGS. 4A-4D in general, and as described above, theexternal fixation system 20 can be configured to stabilize a first bonemember 22 a and a second bone member 22 b relative to each other inaccordance with any suitable embodiment as desired. Thus, the examplesof external fixation systems 20 described herein are presented by way ofexample only. As described above, the first and second bone members 22 aand 22 b can be segments of the same bone, or can be defined differentbones. For instance, the external fixation system 20 can be configuredto stabilize an anatomical joint. Thus, it will be understood that theat least one layer of electrically insulative material 84 can beattached to the external surface of bone anchors of any suitableexternal fixation system as desired.

For instance, as illustrated in FIG. 4A, the external fixation system 20can be configured to stabilize a wrist joint 100. Thus, the externalfixation system 20 can be configured to be secured to a bone in a humanforearm 104, and a bone in a human hand 105 separated by the bone in thehuman forearm by the wrist joint 100. Thus, the first bone member 22 acan be defined by the bone in the human forearm 104, and the second bonemember 22 b can be defined by the bone in the human hand 105. The bonegap 22 c disposed between the first and second bone members 22 a and 22b can be defined by the wrist joint 100. For instance, the first bonemember 22 a can be defined by the radius 108, and the second bone member22 b can be defined by a metacarpal bone 110. The metacarpal bone 110can, for instance, be defined by the index finger 112. As describedabove, the external fixation system 20 can include a first at least oneexternal fixation bone anchor 24 configured to attach to the first bonemember 22 a, and a second at least one external fixation bone anchor 26configured to attach to the second bone member 22 b. In accordance withthe illustrated embodiment, the at least one bone anchor 24 can includefirst and second bone anchors 24 a and 24 b that are configured toattach to the first bone member 22 a. The at least one bone anchor 26can include first and second bone anchors 26 a and 26 b that areconfigured to attach to the second bone member 22 b. The externalfixation system 20 illustrated in FIG. 4A can further include at leastone support rod 38 that extends from a first location aligned with thefirst bone member 22 a, and across the wrist joint 100 to a secondlocation aligned with the second bone member 22 b. The at least onesupport rod 38 is configured to be fixedly secured relative to the firstand second at least one bone anchors 24 and 26. Thus, the support rod 38is configured to extend across the wrist joint 100 at a location outsidethe epidermis. Because the bone anchors 24 and 26 can be fixedly securedto the support rod 38, the bone anchors 24 and 26 can be fixedly securedrelative to each other.

The external fixation system 20 can further include at least one firstclamp 40 configured to secure the at least one support rod 38 to thefirst at least one bone anchor 24. For instance, the first clamp can beconfigured to attach to the support rod 38 and each of the first andsecond bone anchors 24 a and 24 b of the first at least one bone anchor24. The external fixation system 20 can further include at least onesecond clamp 42 configured to secure the at least one support rod 38 tothe second at least one bone anchor 26. For instance, the second clamp42 is configured to attach to the support rod 38 and to each of thefirst and second bone anchors 26 a and 26 b of the second at least onebone anchor 26. It should be appreciated, of course, that the externalfixation system 20 illustrated in FIG. 4A, and all external fixationsystems 20 described herein, can include any number of clamps 40 and 42as desired to secure the at least one support rod 38 to the first andsecond at least one bone anchors 24 and 26. It should be appreciatedthat at least one or both of the first and second bone anchors 24 a and24 b along with one or both of the first and second bone anchors 26 aand 26 b can include the electrically insulative material 84 asdescribed above.

Referring now to FIG. 4B, the external fixation system 20 can beconfigured to stabilize an ankle joint 120. Thus, the external fixationsystem 20 can be configured to be secured to a bone in a human lower leg122, and a bone in a human foot 124 separated by the bone in the humanlower leg 122 by the ankle joint 120. Thus, the first bone member 22 acan be defined by the bone in the human lower leg 122, and the secondbone member 22 b can be defined by the bone in the human foot 124. Thebone gap 22 c disposed between the first and second bone members 22 aand 22 b can be defined by the ankle joint 120. For instance, the firstbone member 22 a can be defined by the tibia 126, and the second bonemember 22 b can be defined by the calcaneus 128. As described above, thefirst at least one external fixation bone anchor 24 is configured toattach to the first bone member 22 a, and the second at least oneexternal fixation bone anchor 26 is configured to attach to the secondbone member 22 b. In accordance with the illustrated embodiment, thefirst at least one bone anchor 24 can include first and second boneanchors 24 a and 24 b that are configured to attach to the first bonemember 22 a. The second at least one bone anchor 26 can include firstand second bone anchors 26 a and 26 b that are configured to attach tothe second bone member 22 b. Thus, the first and second bone anchors 24a and 24 b of the first at least one bone anchor 24 can be configured toattach to the tibia 126. The first and second bone anchors 26 a and 26 bof the second at least one bone anchor 26 can be configured to attach tothe calcaneus 128. For instance the first and second bone anchors 26 aand 26 b can extend out from the calcaneus 128 along substantiallyopposite direction from each other along a medial-lateral direction.

The external fixation system 20 illustrated in FIG. 4B can furtherinclude a first at least one clamp 40 that is configured to attach tothe first at least one bone anchor 24. For instance, the first clamp 40can be configured to attach to each of the first and second bone anchors24 a and 24 b. The external fixation system 20 illustrated in FIG. 4Bcan further include a second at least one clamp 42 that is configured toattach to the second at least one bone anchor 26. For instance, thesecond at least one clamp 42 can include a first clamp 42 a that isconfigured to attach to the first bone anchor 26 a, and a second clamp42 b that is configured to attach to the second bone anchor 26 b. Theexternal fixation system 20 illustrated in FIG. 4B can further include afirst support rod 38 a that is configured to be attached to the firstclamp 40 and the first clamp 42 a of the second at least one clamp 42,thereby securing the first bone anchor 26 a to the first and second boneanchors 24 a and 24 b. The external fixation system 20 illustrated inFIG. 4B can further include a second support rod 38 b that is configuredto be attached to the first clamp 40 and the second clamp 42 b of thesecond at least one clamp 42, thereby securing the second bone anchor 26b to the first and second bone anchors 24 a and 24 b. Thus, the at leastone first clamp 40, the at least one second clamp 42, and the first andsecond support rods 38 a and 38 b are configured to stabilize and secureall of the at least one first and second bone anchors 24 and 26 withrespect to each other. It should be appreciated that the first andsecond support rods 38 a and 38 b are configured to extend across theankle joint 120 at a location outside the epidermis. Because the boneanchors 24 and 26 can be fixedly secured to the first and second supportrods 38 a and 38 b, the bone anchors 24 and 26 can be fixedly securedrelative to each other. It should be appreciated that at least one orboth of the first and second bone anchors 24 a and 24 b along with bothof the first and second bone anchors 26 a and 26 b can include theelectrically insulative material 84 as described above.

Referring now to FIG. 4C, the external fixation system 20 can beconfigured to stabilize a knee joint 140. Thus, the external fixationsystem 20 can be configured to be secured to a bone in a human upper leg142, and a bone in a human lower leg 143 separated by the bone in theupper leg 142 by the knee joint 140. Thus, the first bone member 22 acan be defined by the bone in the human upper leg 142, and the secondbone member 22 b can be defined by the bone in the human lower leg 143.The bone gap 22 c disposed between the first and second bone members 22a and 22 b can be defined by the knee joint 140. For instance, the firstbone member 22 a can be defined by the femur 146, and the second bonemember 22 b can be defined by the tibia 148. Thus, the first bone member22 a can be defined by the bone in the human upper leg 142, and thesecond bone member 22 b can be defined by the bone in the human lowerleg 143. As described above, the first at least one external fixationbone anchor 24 can be configured to attach to the first bone member 22a, and the second at least one external fixation bone anchor 26 can beconfigured to attach to the second bone member 22 b. In accordance withthe illustrated embodiment, the at least one bone anchor 24 can includefirst and second bone anchors 24 a and 24 b that are configured toattach to the first bone member 22 a. The at least one bone anchor 26can include first and second bone anchors 26 a and 26 b that areconfigured to attach to the second bone member 22 b. Thus, the first andsecond bone anchors 24 a and 24 b of the first at least one bone anchor24 can be configured to attach to the femur 146. The first and secondbone anchors 26 a and 26 b of the second at least one bone anchor 26 canbe configured to attach to the tibia 148.

The first at least one clamp 40 of the external fixation system 20illustrated in FIG. 4C can be configured to attach to the first at leastone bone anchor 24. For instance, the first clamp 40 can be configuredto attach to each of the first and second bone anchors 24 a and 24 b.The second at least one clamp 42 of the external fixation system 20illustrated in FIG. 4C can be configured to attach to the second atleast one bone anchor 26. For instance, the second clamp 42 can beconfigured to attach to the first and second bone anchors 26 a and 26 b.The external fixation system 20 illustrated in FIG. 4C can furtherinclude a first support rod 38 a that is configured to be attached tothe first clamp 40, and a second support rod 38 b that is configured tobe attached to the second clamp 42. The external fixation system canfurther include a third clamp 48 that is configured to attach to each ofthe first and second support rods 38 a and 38 b, thereby securing thefirst and second bone anchors 24 a and 24 b of the first at least boneanchor 24 to the first and second bone anchors 26 a and 26 b of thesecond at least one bone member 26. Thus, the at least one first clamp40, the at least one second clamp 42, the third clamp 48, and the firstand second support rods 38 a and 38 b are configured to stabilize andsecure all of the first and second at least one bone anchors 24 and 26with respect to each other. It should be appreciated that the first andsecond support rods 38 a and 38 b and the third clamp 48 define aconstruct that is configured to extend across the knee joint 140 at alocation outside the epidermis. Because the bone anchors 24 and 26 canbe fixedly secured to the first and second support rods 38 a and 38 b,and the first and second support rods 38 a and 38 b can be fixedrelative to each other, the bone anchors 24 and 26 can be fixedlysecured relative to each other. It should be appreciated that at leastone or both of the first and second bone anchors 24 a and 24 b alongwith both of the first and second bone anchors 26 a and 26 b can includethe electrically insulative material 84 as described above.

Referring now to FIG. 4D, the external fixation system 20 can beconfigured to stabilize a sacroiliac joint 160. Thus, the externalfixation system 20 can be configured to be secured to a first sacrum 142and a second sacrum 144 so as to secure and stabilize the first andsecond sacra 142 and 144 with respect to each other. Thus, the firstbone member 22 a can be defined by the first sacrum 142, and the secondbone member 22 b can be defined by the second sacrum 144. The bone gap22 c disposed between the first and second bone members 22 a and 22 bcan be defined by the sacroiliac joint 160. In accordance with theillustrated embodiment, the first at least one bone anchor 24 caninclude first and second bone anchors 24 a and 24 b that are configuredto attach to the first bone member 22 a. The second at least one boneanchor 26 can include first and second bone anchors 26 a and 26 b thatare configured to attach to the second bone member 22 b. Thus, the firstand second bone anchors 24 a and 24 b can be configured to attach to thefirst sacrum 142. The first and second bone anchors 26 a and 26 b can beconfigured to attach to the second sacrum.

The external fixation system 20 illustrated in FIG. 4D can furtherinclude first and second rods 38 a and 38 b that are configured to besecured to the first and second at least one bone anchors 24 and 26,respectively. The external fixation system 20 can further include athird rod 38 c that is configured to be secured to the first rod 38 a.The external fixation system 20 can further include a fourth rod 38 dthat is configured to be secured to the second rod 38 b. The third andfourth rods 38 c and 38 d are further configured to be secured to eachother. For instance, the external fixation system 20 can include a firstat least one clamp 40 that is configured to attach to the first at leastone bone anchor 24. For instance, the first at least one clamp 40 caninclude a first clamp 40 a that is configured to attach to the firstbone anchor 24 a, and a second clamp 40 b that is configured to attachto the second bone anchor 24 b. Each of the first and second clamps 40 aand 40 b is further configured to attach to the first rod 38 a. Theexternal fixation system 20 can include a second at least one clamp 42that is configured to attach to the first at least one bone anchor 24.For instance, the second at least one clamp 42 can include a first clamp42 a that is configured to attach to the first bone anchor 26 a, and asecond clamp 42 b that is configured to attach to the second bone anchor26 b. Each of the first and second clamps 42 a and 42 b is furtherconfigured to attach to the second rod 38 b. The external fixationsystem 20 can further include a third at least one clamp 48. The thirdat least one clamp 48 can include a first clamp 48 a that is configuredto attach to the first rod 38 a and the third rod 38 c so as to securethe first rod 38 a to the third rod 38 c. The third at least one clamp48 can include a second clamp 48 b that is configured to attach to thesecond rod 38 b and the fourth rod 38 d so as to secure the second rod38 b to the fourth rod 38 d. The third at least one clamp 48 can includea third clamp 48 c that is configured to attach to the third rod 38 cand the fourth rod 38 d so as to secure the third rod 38 c to the fourthrod 38 d. Thus, the first at least one bone anchor 24 is secured to thesecond at least one bone anchor 26, thereby stabilizing the first sacrum142 with respect to the second sacrum 144.

Referring to now FIG. 5A, it has been found that when the externalfixation system is placed in a magnetic field having a field strength ofsubstantially 1.5 Tesla, and radio frequency pulses are introduced intothe magnetic field, of instance of the type generated during MRIimaging, none of the threaded regions 34 of the bone anchors 24 and 26increases in temperature in a significant way (e.g., by more than sixdegrees Celsius) that would cause discomfort to the patient or necrosisto the anatomical tissue that surrounds the bone anchors. In fact,testing has shown little or no temperature increases 34. Thus, the tape86 can be said to provide radio frequency shielding of the correspondingbone anchor between the respective shaft and the respective threadedregion 34 in an external fixation system.

Thus, a method can be provided for imaging a region of human anatomy 104that includes the bone 22. The method can include the step of placingthe human anatomy, and thus the bone 22, into an interior of an MRI tube106 having a magnetic field of between 1.5 Tesla and 3.0 Tesla. The bone22 defines first and second bone members 22 a and 22 b to whichrespective threaded regions of first and second bone anchors 24 and 26are anchored. Each of the first and second bone anchors 24 and 26 areattached to at least one support rod 38 via respective first and secondclamps 40 and 42. Each of the bone anchors includes an unthreadedelectrically conductive shaft 30 extending from the respective threadedregions, and an electrically insulative tape wrapped around at least aportion of each of the shafts. The method can further include the stepof directing radio frequency pulses into the interior of the MRI tube soas to provide magnetic resonance images of the human anatomy, whereinthe threaded regions of the bone anchors 24 and 26 do not increase intemperature by more than six degrees Celsius.

As further illustrated in FIGS. 5A-5B, a method can be provided forimaging a region of human anatomy. The method can include the step ofplacing at least a portion of the human anatomy into an interior of theMRI tube 106 that has a magnetic field of approximately 1.5 Tesla. Thehuman anatomy can include at least one bone to which the externalfixation system 20 constructed as recited in accordance with anyembodiment herein. The method can further include the step of directingradio frequency pulses into the interior of the MRI tube 106, whereinthe threaded regions of the first and second at least one bone anchors24 and 26 do not increase in temperature by more than six degreesCelsius. It should be appreciated that the at least a portion of thehuman anatomy includes the at least one bone, such that placing stepincludes placing at least a portion of the external fixation system inthe interior of the MRI tube 106. For instance, the placing step caninclude placing an entirety of the external fixation system 20 in theinterior of the MRI tube 106. Alternatively, the at least a portion ofthe human anatomy does not include the at least one bone, such that theplacing step comprises placing an entirety of the external fixationsystem 20 outside the interior of the MRI tube 106. After the placingstep, the method can further include the step of directing radiofrequency pulses into the interior of the MRI tube so as to providemagnetic resonance images of the region of human anatomy, wherein thethreaded regions of the bone anchors 24 and 26 do not increase intemperature by more than six degrees Celsius.

Without being bound by theory, it is believed that the bone anchors ofconventional external fixation systems can be heated from threedifferent mechanisms, including 1) eddy currents, 2) RF resonance, and3) induction loops. With respect to RF resonance, it is believed thatbone anchor heating by eddy currents of conventional external fixationsystems can generate only a few degrees Celsius temperature rise. It isfurther believed that the electrically insulting polyimide tape disruptsboth RF resonance and the formation of induction loops. Without beingbound by theory, it is postulated that the electrically insulativematerial 84 can have a sufficiently high dielectric constant on the boneanchors 24 so as to isolate the standing RF wave pattern that resonateson the exterior conducting surface 34 of the bone anchors. Thus, it ispostulated that a highly insulating material like polyimide can storeelectrical energy like a capacitor, the electrical current can oscillatewithin the capacitor, and electrical current will be disrupted, therebyeliminating RF heating at the threaded region 34 and the tip 35.Experiments have shown that a polyimide insulator can block current flowup to 3000 volts and is, therefore, capable of insulating the electricalflow responsible for RF resonance heating during magnetic resonanceimaging. MRI. With respect to induction loops, and again without beingbound by theory, it is believed that the polyimide insulator also canprovide a low capacitance to limit the RF electrical current flowing asa loop defined by first and second Schanz screws, a support rod, clampsthat secure the Schanz screws to the support rod, and the anatomicaltissue that receives the bone anchors. This was evaluated by measuringthe temperature rise for an external fixation system having theinsulating polyimide tape applied to the first Schanz screw and noinsulating polyimide tape applied to the second Schanz screw. Notemperature rise was recorded at the tip of the Schanz screw thatincluded the polyimide tape, but a temperature rise was recorded at thetip of the Schanz screw that was not taped. Accordingly, it is believedthat a conductive current loop was present when only one Schanz screwincluded the polyimide electrical insulator.

While the foregoing description and drawings represent the preferredembodiments of the present invention, it will be understood that variousadditions, modifications, combinations and/or substitutions may be madetherein without departing from the spirit and scope of the invention asdefined in the accompanying claims. In particular, it will be clear tothose skilled in the art that the invention may be embodied in otherspecific forms, structures, arrangements, proportions, and with otherelements, materials, and components, without departing from the spiritor essential characteristics thereof. One skilled in the art willappreciate that the invention may be used with many modifications ofstructure, arrangement, proportions, materials, and components, whichare particularly adapted to specific environments and operativerequirements without departing from the principles of the invention. Forinstance, while the bone anchors 24 and 26 have been identified asSchanz screws in accordance with one embodiment, it is contemplated thatthe electrically insulative material 84 can be applied to any suitablealternative bone anchor of other types of implant assemblies, includingK-wires, Steinmann pins, cranial fixation members, cranial tractiontongs, and bone member transport devices (for instance Ilizarov type).Furthermore, it should be appreciated that the electrically insulativematerial 84 can be configured as, or included in, a paint, a polymer, aceramic, and a composite. Thus, the electrically insulative material 84can be applied to the bone anchors, for instance Schanz screws, K-wires,and Steinmann pins, by conventional spraying, dipping, fluidized bed,electrostatic spraying, or any suitable alternative deposition method.Furthermore, the electrically conductive material 84 can bepre-fabricated into a tube that is then received by the at least aportion of the external surface 32 of the shaft 30. In addition,features described herein may be used singularly or in combination withother features. For example, features described in connection with oneembodiment may be used and/or interchanged with features described inanother embodiment. The presently disclosed embodiments are therefore tobe considered in all respects as illustrative and not restrictive, thescope of the invention being indicated by the appended claims, and notlimited to the foregoing description.

It will be appreciated by those skilled in the art that variousmodifications and alterations of the invention can be made withoutdeparting from the broad scope of the appended claims. Some of thesehave been described above and others will be apparent to those skilledin the art.

1. An external fixation system configured to stabilize a wrist joint,the external fixation system comprising: a first external fixation boneanchor including a first shaft defining a first external surface that isdevoid of threads, the first external fixation bone anchor furtherincluding a first threaded region that extends from the first shaft, thefirst threaded region presenting external threads that are configured tobe anchored into a forearm bone, the first external fixation anchorincluding an electrically insulative material that is attached to atleast a portion of the first external surface and that is not attachedto the first threaded region; a second external fixation bone anchordefining a second shaft having a second external surface that is devoidof threads, the second external fixation bone anchor further defining asecond threaded region that extends from the second shaft, the secondthreaded region presenting external threads that are configured to beanchored into a hand bone; a support rod comprising an electricallyconductive material; a first clamp configured to attach to both thefirst shaft and the support rod; and a second clamp configured to attachto both the second shaft and the support rod, wherein the externalfixation system is configured such that when the first clamp is attachedto both the first shaft and the support rod, and when the second clampis attached to both the second shaft and the support rod: 1) each of thefirst and second external fixation bone anchors is fixedly supportedrelative to the support rod, and 2) the wrist joint which is positionedbetween the forearm bone and the hand bone is stabilized.
 2. Theexternal fixation system as recited in claim 1, wherein the first andsecond external fixation bone anchors comprise Schanz screws.
 3. Theexternal fixation system as recited in claim 2, wherein the electricallyinsulative material is adhesively attached to the at least a portion ofthe external surface of the first shaft.
 4. The external fixation systemas recited in claim 3, wherein the electrically insulative material isconfigured as a tape having a substrate made from the electricallyinsulative material, and an adhesive disposed on one surface of thesubstrate, such that the adhesive attaches the tape to the at least aportion of the external surface of the first shaft. 5-9. (canceled) 10.The external fixation system as recited in claim 4, wherein the externalfixation system is configured to be placed in a magnetic field having afield strength of approximately 1.5 Tesla, and the external fixationsystem is further configured such that when radio frequency pulses areintroduced into the magnetic field, neither the first threaded regionnor the second threaded region increases in temperature by more than sixdegrees Celsius. 11-20. (canceled)
 21. An external fixation systemconfigured to stabilize an ankle joint, the external fixation systemcomprising: a first external fixation bone anchor including a firstshaft defining a first external surface that is devoid of threads, thefirst external fixation bone anchor further including a first threadedregion that extends from the first shaft, the first threaded regionpresenting external threads that are configured to be anchored into alower leg bone, the first external fixation anchor including anelectrically insulative material that is attached to at least a portionof the first external surface and that is not attached to the firstthreaded region; a second external fixation bone anchor defining asecond shaft having a second external surface that is devoid of threads,the second external fixation bone anchor further defining a secondthreaded region that extends from the second shaft, the second threadedregion presenting external threads that are configured to be anchoredinto a foot bone; a support rod comprising an electrically conductivematerial; a first clamp configured to attach to both the first shaft andthe support rod; and a second clamp configured to attach to both thesecond shaft and the support rod, wherein the external fixation systemis configured such that when the first clamp is attached to both thefirst shaft and the support rod, and when the second clamp is attachedto both the second shaft and the support rod: 1) each of the first andsecond external fixation bone anchors is fixedly supported relative tothe support rod, and 2) the ankle joint which is positioned between thelower leg bone and the foot bone is stabilized.
 22. The externalfixation system as recited in claim 21, wherein the support rod is afirst support rod, and the foot bone is a first foot bone, the externalfixation system comprising: a third external fixation bone anchordefining a third shaft having a third external surface that is devoid ofthreads, the third external fixation bone anchor further defining athird threaded region that extends from the third shaft, the thirdthreaded region presenting external threads that are configured to beanchored into a second foot bone; a second support rod comprising anelectrically conductive material; and a third clamp configured to attachto both the third shaft and the second support rod, wherein the externalfixation system is configured such that when the first clamp is attachedto both the first shaft and the second support rod, and when the thirdclamp is attached to both the third shaft and the second support rod: 1)each of the first and third external fixation bone anchors is fixedlysupported relative to the second support rod.
 23. The external fixationsystem as recited in claim 22, wherein the first foot bone is differentthan the second foot bone.
 24. The external fixation system as recitedin claim 21, wherein the electrically insulative material is configuredas a tape having a substrate made from the electrically insulativematerial, and an adhesive disposed on one surface of the substrate, suchthat the adhesive attaches the tape to the at least a portion of theexternal surface of the first shaft.
 25. The external fixation system asrecited in claim 24, wherein the external fixation system is configuredto be placed in a magnetic field having a field strength ofapproximately 1.5 Tesla, and the external fixation system is furtherconfigured such that when radio frequency pulses are introduced into themagnetic field, neither the first threaded region nor the secondthreaded region increases in temperature by more than six degreesCelsius.
 26. An external fixation system configured to stabilize a kneejoint, the external fixation system comprising: a first externalfixation bone anchor including a first shaft defining a first externalsurface that is devoid of threads, the first external fixation boneanchor further including a first threaded region that extends from thefirst shaft, the first threaded region presenting external threads thatare configured to be anchored into an upper leg bone, the first externalfixation anchor including an electrically insulative material that isattached to at least a portion of the first external surface and that isnot attached to the first threaded region; a second external fixationbone anchor defining a second shaft having a second external surfacethat is devoid of threads, the second external fixation bone anchorfurther defining a second threaded region that extends from the secondshaft, the second threaded region presenting external threads that areconfigured to be anchored into a lower leg bone; at least one supportrod comprising an electrically conductive material; a first clampconfigured to attach to both the first shaft and the at least onesupport rod; and a second clamp configured to attach to both the secondshaft and the at least one support rod; wherein the external fixationsystem is configured such that when the first clamp is attached to boththe first shaft and the at least one support rod, and when the secondclamp is attached to both the second shaft and the at least one supportrod: 1) each of the first and second external fixation bone anchors isfixedly supported relative to the at least one support rod, and 2) theknee joint which is positioned between the upper leg bone and the lowerleg bone is stabilized.
 27. The external fixation system as recited inclaim 26, wherein the at least one support rod includes a first supportrod and a second support rod, the external fixation system comprising athird clamp configured to attach to both the first support rod and thesecond support rod, wherein the external fixation system is configuredsuch that the first clamp is configured to attach to both the firstshaft and the first support rod, the second clamp is configured toattach to both the second shaft and the second support rod, and thethird clamp is configured to attach to both the first support rod andthe second support rod.
 28. The external fixation system as recited inclaim 27, wherein the first support rod is nonparallel to the secondsupport rod.
 29. The external fixation system as recited in claim 26,wherein the electrically insulative material is configured as a tapehaving a substrate made from the electrically insulative material, andan adhesive disposed on one surface of the substrate, such that theadhesive attaches the tape to the at least a portion of the externalsurface of the first shaft.
 30. The external fixation system as recitedin claim 29, wherein the external fixation system is configured to beplaced in a magnetic field having a field strength of approximately 1.5Tesla, and the external fixation system is further configured such thatwhen radio frequency pulses are introduced into the magnetic field,neither the first threaded region nor the second threaded regionincreases in temperature by more than six degrees Celsius.
 31. Anexternal fixation system configured to stabilize a sacroiliac joint, theexternal fixation system comprising: a first external fixation boneanchor including a first shaft defining a first external surface that isdevoid of threads, the first external fixation bone anchor furtherincluding a first threaded region that extends from the first shaft, thefirst threaded region presenting external threads that are configured tobe anchored into a first sacrum, the first external fixation anchorincluding an electrically insulative material that is attached to atleast a portion of the first external surface and that is not attachedto the first threaded region; a second external fixation bone anchordefining a second shaft having a second external surface that is devoidof threads, the second external fixation bone anchor further defining asecond threaded region that extends from the second shaft, the secondthreaded region presenting external threads that are configured to beanchored into a second sacrum; at least one support rod comprising anelectrically conductive material; a first clamp configured to attach toboth the first shaft and the at least one support rod; and a secondclamp configured to attach to both the second shaft and the at least onesupport rod; wherein the external fixation system is configured suchthat when the first clamp is attached to both the first shaft and the atleast one support rod, and when the second clamp is attached to both thesecond shaft and the at least one support rod: 1) each of the first andsecond external fixation bone anchors is fixedly supported relative tothe at least one support rod, and 2) the sacroiliac joint which ispositioned between the first sacrum and the second sacrum is stabilized.32. The external fixation system as recited in claim 31, wherein the atleast one support rod includes a first support rod, a second supportrod, a third support rod, and a fourth support rod, the externalfixation system comprising: a third clamp configured to attach to boththe first support rod and the third support rod; a fourth clampconfigured to attach to both the second support rod and the fourthsupport rod; and a fifth clamp configured to attach to both the thirdsupport rod and the fourth support rod, wherein the external fixationsystem is configured such that the first clamp is configured to attachto both the first shaft and the first support rod, and the second clampis configured to attach to both the second shaft and the second supportrod.
 33. The external fixation system as recited in claim 32, whereinthe third support rod is nonparallel to the fourth support rod.
 34. Theexternal fixation system as recited in claim 31, wherein theelectrically insulative material is configured as a tape having asubstrate made from the electrically insulative material, and anadhesive disposed on one surface of the substrate, such that theadhesive attaches the tape to the at least a portion of the externalsurface of the first shaft.
 35. The external fixation system as recitedin claim 34, wherein the external fixation system is configured to beplaced in a magnetic field having a field strength of approximately 1.5Tesla, and the external fixation system is further configured such thatwhen radio frequency pulses are introduced into the magnetic field,neither the first threaded region nor the second threaded regionincreases in temperature by more than six degrees Celsius.